Humidification system

ABSTRACT

A humidification system has a humidification source and a main gases flow path. The main gases flow path has a low pressure region and a high pressure region. In some embodiments, each of the low pressure region and the high pressure region has an aperture. The pressure difference between the apertures promotes a gases flow between the main gases flow path and the humidification source, and results in humidifying the gases in the main gases flow path.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Technical Field

The present disclosure generally relates to respiratory gas therapy.More particularly, the present disclosure relates to a system for thehumidification of respiratory gases for use with respiratory gas therapysystems.

Description of Related Art

Respiratory disorders deal with the inability of a sufferer to effect asufficient exchange of gases with the environment, leading to animbalance of gases in the sufferer. These disorders can arise as apathological consequence of an obstruction of the airway, insufficiencyof the lungs in generating negative pressure, an irregularity in thenervous function of the brain stem, or some other physiologicalcomplication. Treatment of such disorders is diverse and depends on theparticular respiratory disorder being targeted. In the first instance, aconstriction of the airway, otherwise known as an obstructive apnea or ahypopnea (collectively referred to as obstructive sleep apnea or OSA),can occur when the muscles that normally keep the airway open in apatient relax during slumber to the extent that the airway isconstrained or completely closed off, a phenomenon often manifestingitself in the form of snoring. When this occurs for a significant periodof time, the patient's brain typically recognizes the threat of hypoxiaand partially wakes the patient in order to open the airway so thatnormal breathing may resume. The patient may be unaware of theseoccurrences, which may occur as many as several hundred times persession of sleep. This partial awakening may significantly reduce thequality of the patient's sleep, over time potentially leading to avariety of symptoms, including chronic fatigue, elevated heart rate,elevated blood pressure, weight gain, headaches, irritability,depression and anxiety.

Obstructive sleep apnea is commonly treated with the application ofpositive airway pressure (PAP) therapy. PAP therapy involves deliveringa flow of gas to a patient at a therapeutic pressure above atmosphericpressure that may reduce the frequency and/or duration of apneas,hypopneas, and/or flow limitations. This therapy may be delivered byusing a positive airway pressure device (PAP device or blower) to propela pressurized stream of air through a conduit to a patient through aninterface or mask located on the face of the patient.

The stream of air may be heated to near body temperature. The stream ofair may be humidified. The humidification may be performed by forcingthe stream of air to travel through a respiratory humidifier containingwater and a heater for heating the water. In such a system the heaterencourages the evaporation of the water, which in turn partially orfully imbues the stream of air with moisture and/or heat. This moistureand/or heat may help to ameliorate discomfort that may arise from theuse of un-humidified PAP therapy.

The entire gases flow may be passed through a humidifier in order tohumidify the gases. For example the entire gases flow may pass through ahumidifier chamber. The humidification chamber may comprise baffles orother features to create turbulence in the gases flow. There may be asubstantial pressure drop across the chamber. The magnitude of thepressure drop across the chamber may vary and is dependent on the flowrate and the level of water in the chamber. The variability in themagnitude of the pressure drop may make it difficult to ensure aconstant pressure is provided to a patient across all flow rates andhumidification chamber water levels.

BRIEF SUMMARY

The systems, methods and devices described herein have innovativeaspects, no single one of which is indispensable or solely responsiblefor their desirable attributes. Without limiting the scope of theclaims, some of the advantageous features will now be summarized.

A humidification system may comprise a main gases flow path and ahumidification source. The main gases flow path may comprise a gasesinlet and a gases outlet. The main gases flow path may comprise regionsof relatively high pressure and/or regions of relatively low pressure.Substantially at, or near, to these regions of relatively high and lowpressure are inlet and/or outlet apertures. These apertures may providefor a pneumatic connection with a gases space in the humidificationsource.

The apertures generate gases flow either from the main gases flow pathinto the humidification source or, from the humidification source intothe main gases flow path. The direction of the gases flow may bedependent on whether the aperture is near a region of the gases flowpath that is of a relatively high pressure or a relatively low pressure.An aperture near an area of relatively high pressure generates a flow ofgases out of the main gases flow path and is an outlet aperture. Anaperture near an area of relatively low pressure generates a flow ofgases into the main gases flow path and is an inlet aperture. In someembodiments the humidification source comprises a humidificationchamber. The humidification chamber is configured to providehumidification to gases in a gases space of the humidification chamber.The apertures generate gases flow either from the main gases flow pathinto the humidification chamber or, from the humidification chamber intothe main gases flow path.

The regions of relatively high and low pressure can be generated by achange in cross sectional area of the main gases flow path or, featuresin the main gases flow path. The main gases flow path may comprise aseries of inlet and/or outlet apertures, which generate a secondarygases flow through the humidification chamber. The secondary gases flowmay be flow from the main gases flow, through an outlet aperture(s),through the gases space of the humidification chamber and through aninlet aperture back into the gases flow path.

The direction of this secondary gases flow may be in substantially thesame direction or an opposite direction to the gases flow. The directionof the secondary gases flow is dependent on the relative positions ofthe inlet and outlet apertures along the gases flow path. For example ifthe inlet aperture(s) is/are located prior to the outlet aperture(s),then the secondary gases flow will be in the substantially the samedirection as the main gases flow. If the outlet aperture(s) is/arelocated prior to the inlet aperture(s) then the secondary gases flowwill be in substantially the opposite direction to the main gases flow.If the secondary gases flow is in the opposite direction to the maingases flow the main gases flow may be recirculated, at least to anextent, through the humidification chamber.

In accordance with a first aspect of at least one embodiment disclosedherein, a humidification system comprises:

a humidification source configured to humidify gases,

a main gases flow path comprising a low pressure region, and a highpressure region,

wherein the main gases flow path comprises an outlet aperture near thehigh pressure region, the outlet aperture pneumatically connected to thehumidification source to allow a flow of gases from the main gases flowpath into the humidification source, and

wherein the main gases flow path comprises an inlet aperture near thelow pressure region, the inlet aperture pneumatically connected to thehumidification source to allow a flow of gases from the humidificationsource into the main gases flow path.

In some embodiments, the humidification source comprises ahumidification chamber.

In some embodiments, the outlet aperture is located downstream to theinlet aperture along the main gases flow path.

In some embodiments, the outlet aperture is located upstream to theinlet aperture along the main gases flow path.

In some embodiments, the main gases flow path further comprises a neckportion, an inlet portion and an outlet portion, wherein the neckportion is of a smaller cross sectional area than the inlet and/oroutlet portions.

In some embodiments, the outlet aperture is located near at least one ofthe inlet portion and/or the outlet portion.

In some embodiments, the humidification chamber is sealed to an externalenvironment.

In some embodiments, the humidification chamber comprises a valve or anaperture configured to allow gas exchange with an external environment.

In some embodiments, the valve or the aperture is configured to onlyallow gases from the external environment into the humidificationchamber.

In some embodiments, a flow of gases from the humidification source tothe main gases flow path is between 0% and 40%, or between 10% and 30%,or is about 20% or is about 10% of a flow of gases through the maingases flow path.

In some embodiments, the humidification chamber further comprises aheater configured to heat the humidification chamber, wherein the heateris a heater plate.

In some embodiments, the cross sectional area of a part of the maingases flow path is variable.

In some embodiments, the cross sectional area of a part of the neckportion, inlet portion and/or outlet portion is variable.

In some embodiments, the main gases flow path comprises a valve, thevalve configured to vary the flow rate of gases through the main gasesflow path.

In some embodiments, the main gases flow path comprises a featureconfigured to change at least one of pressure, velocity, flow rate and aflow profile of the flow of gases through the main gases flow path.

In some embodiments, the feature is at least one of a baffle, diffuser,orifice plate, or texture on the surface of the main gases flow path.

In some embodiments, the feature is actuatable to vary at least one ofpressure, velocity, flow rate and a flow profile of the flow of gasesthrough the main gases flow path.

In accordance with a second aspect of at least one embodiment disclosedherein, a humidification system comprises:

a main gases flow path,

a humidification source,

wherein the main gases flow path comprises a first portion and a secondportion,

wherein the first portion comprises a larger cross sectional area thanthe second portion so that with a flow of gases through the main gasesflow path a high pressure region is generated in the first portion and alow pressure region is generated in the second portion, and

an inlet aperture, the inlet aperture being positioned at or near thelow pressure region to allow a gases flow from the humidification sourceto the main gases flow path.

In some embodiments, the gases flow through the main gases flow pathfrom the first portion to the second portion.

In some embodiments, the gases flow through the main gases flow pathfrom the second portion to the first portion.

In some embodiments, the main gases flow path further comprises atransition portion pneumatically connecting the first portion and thesecond portion.

In some embodiments, the inlet aperture is provided at the transitionportion.

In some embodiments, the first portion tapers from a larger crosssection to a smaller cross section at or adjacent to the second portion.

In some embodiments, the first portion is an inlet portion and the gasesflow path further comprises an outlet portion, and wherein the secondportion is a neck portion in between the inlet and outlet portions, theneck portion having a smaller cross sectional area than the inlet andoutlet portions, and

with a flow of gases through the main gases flow path a high pressureregion is generated in the inlet and outlet portions and a low pressureregion is generated in the neck portion.

In some embodiments, the outlet portion tapers from a larger crosssection to a smaller cross section at or adjacent to the neck portion.

In some embodiments, the system further comprises an outlet aperture ator near the high pressure region to allow a flow of gases from the maingases flow path into the humidification source.

In some embodiments, the outlet aperture is adjacent to an inlet or anoutlet of the main gases flow path.

In some embodiments, the outlet aperture is located downstream to theinlet aperture along the main gases flow path.

In some embodiments, the outlet aperture is located upstream to theinlet aperture along the main gases flow path.

In some embodiments, the humidification source comprises a valve or anaperture allowing gas exchange with an external environment.

In some embodiments, the valve or the aperture is configured to onlyallow gases from the external environment into the humidificationchamber.

In some embodiments, the humidification source is sealed from anexternal environment but for a flow path through the source via theoutlet aperture and the inlet aperture.

In some embodiments, a flow of gases from the humidification source tothe main gases flow path is between 0% and 40%, or between 10% and 30%,or is about 20% or is about 10% of a flow of gases through the maingases flow path.

In some embodiments, the cross sectional area of a part of the maingases flow path is variable.

In some embodiments, the cross sectional area of a part of the neckportion, inlet portion and/or outlet portion is variable.

In some embodiments, the system further comprises a valve configured tovary the flow rate of gases through the main gases flow path.

In some embodiments, the main gases flow path comprises a featureconfigured to change at least one of pressure, velocity, flow rate and aflow profile of the flow of gases through the main gases flow path.

In some embodiments, the system comprises a feature between thehumidification source and the main gases flow path, the featureconfigured to change at least one of pressure, velocity, flow rate and aflow profile of a flow of gases from the humidification source to themain gases flow path.

In some embodiments, the feature is at least one of a valve, baffle,diffuser, orifice plate, or texture on the surface of the main gasesflow path or in contact with the flow of gases.

In some embodiments, the feature is actuatable to vary at least one ofpressure, velocity, flow rate and a flow profile of the flow of gasesthrough the main gases flow path

In some embodiments, the humidification source comprises ahumidification chamber.

In some embodiments, the humidification source further comprises aheater configured to heat the humidification chamber. In someembodiments the heater is a heater plate.

In some embodiments, the main gases flow path is formed in a lidcomponent of the humidification chamber or a tubular component passingthrough a gases space of the humidification chamber.

In some embodiments, the system further comprises a connector, theconnector comprising the main gases flow path and a humidification inletportion to connect to a hose or conduit to the humidification source,the humidification inlet portion in communication with the inletaperture.

In some embodiments, the connector is a T or Y connector.

In some embodiments, the inlet aperture comprises an annular cavityextending at least part way around the main gases flow path.

In some embodiments, the annular cavity comprises a toroid cavity with ahalf cylinder cross section opening into the main gases flow pathtowards an inlet end of the main gases flow path

In some embodiments, the system further comprises a structure adapted tocause gases flow from the main gases flow path to swirl.

In some embodiments, the structure comprises one or more vanes orbaffles that interfere with the gases flow to cause the flow to swirl.

In some embodiments, the structure is downstream to the inlet apertureor at or adjacent to an outlet of the main gases flow path.

In accordance with a third aspect of at least one embodiment disclosedherein, a humidification system comprises:

a main gases flow path,

a secondary gases flow path (or a shunt path),

a humidification chamber,

wherein the secondary flow path extends from the main gases flow path,into the humidification chamber and back into the main gases flow path.

In some embodiments, the secondary flow path extends from the main gasesflow into the humidification chamber before the secondary flow pathenters the main gases flow path.

In some embodiments, the secondary flow path extends from the main gasesflow into the humidification chamber after the secondary flow pathenters the main gases flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the drawings, reference numbers can be reused to indicategeneral correspondence between reference elements. The drawings areprovided to illustrate example embodiments described herein and are notintended to limit the scope of the disclosure.

FIG. 1 shows a top view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 2 shows a side view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 3 shows a side view of a cross section of a humidification systemcomprising the main gases flow path of FIGS. 1 and 2 .

FIG. 4 shows a top view of a cross section of a main gases flow pathconfigured to

FIG. 5 shows a side view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 6 shows a side view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 7 shows a side view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 8 shows a side view of a cross section of a humidification systemcomprising the main gases flow path of FIGS. 6 and 7 .

FIG. 9 shows a top view of a cross section of a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 10 shows a side view of a cross section of a humidification systemcomprising a gases flow path configured to generate regions of low andhigh pressure.

FIG. 11 shows a side view of a cross section of a humidification systemcomprising a gases flow path configured to generate regions of low andhigh pressure.

FIG. 12A illustrates a connector comprising a main gases flow pathconfigured to generate regions of low and high pressure.

FIG. 12B is a side view of the connector of FIG. 12A.

FIG. 12C is an end view on an outlet end of the connector of FIG. 12A.

FIG. 12D is a cross sectional view on line I-I in FIG. 12B.

FIG. 12E is a cross sectional view on line II-II in FIG. 12C.

FIG. 12F is a perspective cross sectional view on line II-II in FIG.12C.

FIG. 13 is a schematic of a humidification system according to at leastone embodiment disclosed herein.

DETAILED DESCRIPTION

A humidification system may comprise a main gases flow path and ahumidification source. The main gases flow path may comprise a gasesinlet and a gases outlet. The main gases flow path may comprise regionsof relatively high pressure and/or regions of relatively low pressure.The regions of relatively high pressure and/or regions of relatively lowpressure can be generated by at least one of: a change in crosssectional area of the flow path, a change in the surface of the flowpath, a change in features of the flow path itself (for example, bafflesor fins). The change in pressure may be at least partially recoverableor unrecoverable. If the pressure change is caused by, for example, achange in the flow cross-sectional area, the change may be reversible inthat reversing the change in area will reverse the change in pressure.One such example of a way to change pressure in a recoverable manner isby using a venturi.

Generally, a gases flow may be generated from an area of higher pressureto an area of lower pressure. The gases flow path may comprise at leastone aperture substantially at or near the regions of high or lowpressure. A gases flow may be generated from the at least one aperture;its flow direction being dependent on whether the at least one apertureis substantially near a region of high or low pressure of the gases flowpath. Where the at least one aperture is near a high pressure region theflow direction of gases through the aperture will be from or out of themain gases flow path. Where the at least one aperture is near a lowpressure region the flow direction of gases through the aperture will beinto the main gases flow path. The at least one aperture may provide apneumatic connection between the gases flow path and the humidificationsource allowing a gases flow from the main gases flow path to thehumidification source, and/or from the humidification source to thegases flow path.

In some embodiments the main gases flow path may comprise features tochange the flow characteristics of the gases flow. The features maycomprise at least one of surface features on the surface of the gasesflow path, baffles, an orifice plate, or a diffuser. In some embodimentsthese features may influence the pressure, velocity, or flow profile (interms of which parts of the flow are turbulent or laminar). In someembodiments the features are actuatable such that their effect on thegases flow varies. The features may be actuated to change at least oneof; their angle of attack relative to the gases flow path, or theirgeometric profile or area.

When the terms ‘high pressure’ or ‘relatively high pressure’ are usedthey are to be interpreted as referring to a higher pressure relative toat least one of: the average pressure of the system, the pressure in thehumidification source, or atmospheric pressure.

When the terms ‘low pressure’ or ‘relatively lower pressure’ are usedthey are to be interpreted as referring to a lower pressure relative toat least one of: the average pressure of the system, the pressure in thehumidification source, or atmospheric pressure.

The humidification source is configured to provide humidification togases. In some embodiments the humidification source comprises ahumidification chamber. In some embodiments the humidification chamberadds water vapour to gases in the chamber. The humidification chambermay comprise a heater configured to warm the liquid in thehumidification chamber. In some embodiments the heater comprises aheater plate. In some embodiments the heater is provided within thechamber, or external to the chamber to heat the contents of the chambervia a side or bottom of the chamber.

FIGS. 1 and 2 show a top and side view, respectively, of a main gasesflow path 1 configured to generate regions of low and high pressure. Themain gases flow path 1 comprises an inlet portion 2, a neck 3 and anoutlet portion 4. The main gases flow is indicated by the arrows 11, 12.Gases flow enters the main gases flow path 1 at the gases inlet 6,passes through the inlet portion 2, neck portion 3 and outlet portion 4and exits the main gases flow path 1 at the gases outlet 5. The maingases flow path comprises an outlet aperture 7 and an inlet aperture 8.In some embodiments the outlet aperture 7 is located generally in theinlet portion 2 of the main gases flow path 1. In some embodiments theinlet aperture 8 is located generally in the neck portion 3, the outletportion 4 or a combination thereof. In some embodiments there may bemultiple inlet and/or outlet apertures located in at least one of theinlet portion 2, the neck portion 3 and/or the outlet portion. In someembodiments there is no outlet aperture; instead the humidificationchamber 13 is connected to atmosphere. In these embodiments there isonly an inlet aperture 8 which acts to draw in gases from thehumidification chamber 13. In some embodiments the humidificationchamber is sealed airtight. In some embodiments the humidificationchamber comprises a valve to allow for gas exchange with the externalenvironment. The humidification chamber may comprise a heater plate 15configured to transfer energy to a liquid 14 (for example water).

The relative pressure and velocity of the gases varies along the flowpath 11, 12 and is related to the cross sectional area of the flow pathat a particular point. The relationship between static pressure andvelocity at any point can be determined by a simplified version of theBernoulli equation (assuming there is no change in height of the flowpath.)

$\begin{matrix}{{{\frac{1}{2}\rho v^{2}} + p} = {Constant}} & ( {{Equation}\mspace{20mu} 1} )\end{matrix}$

Where:

v=the velocity of the gas

p=the static pressure at a particular point

ρ=the density of the gas

This equation illustrates that an increase in velocity will lead to adecrease in pressure and vice versa. Therefore for portions of the maingases flow path which have lower velocities relative to other parts ofthe main gases flow path, these portions will have a higher relativestatic pressure.

The relationship between volumetric flow rate, velocity and area can bedescribed by the equation below:

$\begin{matrix}{Q = {vA}} & ( {{Equation}\mspace{20mu} 2} )\end{matrix}$

Where:

Q=Volumetric flow rate

v=the velocity of the gas

A=Cross sectional area

This equation illustrates that if there is constant volumetric flow adecrease in cross sectional area will lead to an increase in velocityand vice versa.

The inlet portion 2 and the outlet portion 4 may have larger crosssectional areas than the neck portion 3. The cross sectional area of theinlet portion 2 tapers from a larger cross section at the gases inlet 6to a smaller cross section where the inlet portion 2 transitions to theneck portion 3. In some embodiments, the neck portion has asubstantially constant cross section for its entire length. In someembodiments the neck portion may be tapered. The taper may increase ordecrease the cross sectional area along the gases flow path. The crosssectional area of the outlet portion 4 tapers from the smaller crosssection where the neck portion 3 transitions to the outlet portion 4, toa larger cross section at the gases outlet 5. The tapers described abovemay be at a constant pitch or the pitch may vary along the taper.

In some embodiments any of the inlet, neck or outlet portions 2,3,4 maycomprise a combination of smaller sub portions of which each maydecrease, increase or remain constant in cross sectional area byaltering the shapes and/or dimensions. In some embodiments, inletportion and the outlet portion have substantially the same crosssectional area. In some embodiments, the inlet portion may have a largercross sectional area than the outlet portion. In other embodiments, theoutlet portion may have a larger cross sectional area than the inletportion.

Applying equation 2 to the main gases flow path 1 of FIG. 1 , the gasespassing through the inlet portion 2 and the outlet portion 4 have alower velocity relative to the velocity of the gases passing though theneck portion 3. Further, then applying equation 1 the gases passingthrough the inlet portion 2 and the outlet portion 4 have a higherpressure relative to the gases passing through the neck portion.

FIG. 3 shows a cross sectional side view of a main gases flow path 1 anda humidification chamber 13. The outlet aperture 7 and inlet aperture 8allow for a pneumatic connection between the main gases flow 11, 12 anda gases space of the humidification chamber 13. In some embodiments, theoutlet aperture 7 and inlet aperture 8 act to provide a shunt (e.g.parallel) or secondary flow path to divert a portion of the gases flow11, 12 in the main gases flow path from the main gases flow path throughthe humidification chamber 13 and back into the main gases flow path. Asthe shunted or secondary flow path gas passes through the humidificationchamber 13, it is humidified. Once the humidified gas rejoins the maingases flow path 1, it mixes with the main gases flow 11, 12. The mixturecomprises the warmed and humidified gas from the shunt or secondary pathand the gas from the main gases flow path 1.

The pressure inside the main gases flow path 1 near the outlet aperture7 is greater than the pressure inside the humidification source 13 andinside the main gases flow path 1 near the inlet aperture 8. Thepressure in the humidification source 13 is greater than the pressureinside the main gases flow path 1 near the inlet aperture 8. Thispressure gradient drives a flow of gas from the main gases flow path 1into the humidification chamber 13 and then back into the main gasesflow path 1. The higher pressure area inside the main gases flow path 1near the outlet aperture 7 drives an outlet gases flow 10 from the maingases flow path 1 into the humidification chamber 13. The low pressurearea inside the main gases flow path near the inlet aperture 8 drives aninlet gases flow 9 from the humidification chamber 13 into the maingases flow path 1.

In some embodiments, the flow rate of the shunted of secondary flow pathgas (the inlet and outlet gases flows) is substantially smaller thanthat of the main gases flow. In some embodiments, the flow rate of theshunted or secondary flow path gas is between 0% and 40% of the maingases flow. In some embodiments, the flow rate of the shunted orsecondary flow path gas is between 10% and 30% of the main gases flow.In some embodiments, the flow rate of the shunted or secondary flow pathgas is 20% or 10% of the main gases flow.

FIGS. 4 and 5 show top and side views, respectively, of an embodiment ofa main gases flow path 101. FIG. 6 shows the main gases flow path 101 aspart of a humidification system. The main gases flow path 101 may be aventuri and may comprise an inlet portion 102, a neck portion 103, andan outlet portion 104. Gases flow into the gases inlet 106 along thegases flow path 111, 112 and out the gases outlet 105. The main gasesflow path 101 also comprises an inlet aperture 108 and an outletaperture 107. In some embodiments, the outlet aperture 107 is locatednear the outlet portion 104 and optionally near the gases outlet 105.The inlet aperture 108 is located near the neck portion 103.

The humidification system may comprise a main gases flow path 101 andthe humidification source may comprise a humidification chamber 113. Thehumidification chamber may comprise a heater plate 115 configured totransfer energy to a liquid 114 (for example, water). Due to thepressure difference between the inlet aperture 108 and outlet aperture107, an inlet gases flow 109 and an outlet gases flow 110 will begenerated. Water vapour is added to the gases flow 110 as it passesthough the humidification chamber. The further humidified gas then flowsthrough the inlet aperture 110 and back into the main gases flow path101.

In some embodiments, such as that shown in FIGS. 4 and 5 , the inletaperture 108 is located before the outlet aperture 107 in the main gasesflow path 101. In these embodiments at least part of the gas in the maingases flow path 101 may be recirculated through the humidificationchamber 113 multiple times.

FIGS. 7 and 8 show side views of a main gases flow path 201 and FIG. 9shows the main gases flow path 201 as part of a humidification system.In some embodiments, the main gases flow path 201 comprises an inletaperture 208 located near the neck portion 203, and is without an outletaperture. In these embodiments, the low pressure area near the inletaperture 208 acts to generate a flow of gases 209 from thehumidification chamber 213 into the main gases flow path 201. In someembodiments, the humidification chamber 213 is not sealed to theexternal environment. This allows for gases to flow from the externalenvironment into the humidification chamber 213 and replace the gas thathas been transferred to the main gases flow 211, 212. Therefore nooutlet aperture is necessary since flow enters the chamber from theatmosphere and not via the main gases flow path. In some embodiments thehumidification source comprises an inlet, allowing a flow of gases toenter the humidification source, the inlet separate from the main gasesflow path so that gases enter the humidification source before enteringthe main gases flow path via the inlet aperture 208.

In some embodiments, the humidification chamber comprises a valveconfigured to allow for a gas exchange between the external environmentand the humidification chamber 213. In some embodiments, the valve is aone way valve that only allows flow of gases into the humidificationchamber 213.

In some embodiments, the pressure at a region of the gases flow path maybe varied. In some embodiments, the pressure near at least the neck,inlet or outlet region(s) is varied. In some embodiments, theorientation of features in the flow path is changed. For example, theangle of a baffle or other feature to the direction of the flow of gasesalong the main flow path may be varied to create an area of low or highpressure. In some embodiments, the cross sectional area of the flow pathcan be varied. The cross sectional area may be varied by, for example, avalve or by compression or deformation of the flow path.

In some embodiments at least part of the main gases flow path may bemade of a malleable material such as a plastic, for example, a rubber ora polymer. Part of the main gases flow path may be deformed under anexternally applied force (e.g. by a screw or other mechanism) such thata cross sectional area of the part of the main gases flow path may bevaried. By varying the cross section of the main gases flow path theproportion of gases flow from the humidification source entering themain gases flow path may be controlled.

In the above described embodiments illustrated in FIGS. 1 to 9 , theinlet portion 2, 102, 202 is a first portion, and the neck portion 3,103, 203 is a second portion. The first portion 2, 102, 103 comprises alarger cross sectional area than the second portion 3, 103, 203 so thatwith a flow of gases 11, 12, 111, 112, 211, 212 through the main gasesflow path 1, 101, 201 a high pressure region is generated in the firstportion 2, 102, 103 and a low pressure region is generated in the secondportion 3, 103, 203. The inlet aperture 8, 108, 208 is located near to(e.g. close to or in) the second portion 3, 103, 203 so that the inletaperture is near to or in the low pressure region. The low pressureregion has a pressure less than a pressure of the humidification source,such that a pressure gradient is created between the humidificationsource and the low pressure region, causing a flow from thehumidification source to the main gases flow path. In the embodiment ofFIGS. 7 to 9 , the inlet aperture is illustrated as being near to andslightly downstream of the neck or second portion of the main gases flowpath. Alternatively, the inlet aperture may be in or slightly upstreamof the neck or second portion.

FIG. 10 shows an embodiment comprising a humidification chamber 313 anda main gases flow path 301. The main gases flow path 301 comprisesfeatures configured to generate a gases flow 310 from the humidificationchamber 313 into the main gases flow 311, 312. The main gases flow path301 comprises a gases inlet 306, a first portion 302, a second portion304, a third portion 303, and a gases outlet 305. Gases flow into thegases inlet 306, pass through the first portion to the second portionvia the third portion and out the gases outlet 305.

The cross sectional area of the first portion 302 is greater than thatof the second portion 304. Therefore, the velocity of the main gasesflow 311, 312 is greater in the second portion 304 than it is in thefirst portion 302. This means the pressure in the second portion 304 islower than the pressure in the first portion 302. This lower pressureregion generates a gases flow 310 from the humidification chamber 313into the main gases flow path 301. The gases flow 310 may contain watervapour provided to the gases flow 310 in the humidification chamber 313.The third portion 303 is of a funnel type shape and acts to transitionthe main gases flow 311, 312 from the first portion 302 to the secondportion 303 and to provide a path for the gases flow 310 from thehumidification chamber. The third portion 303 may be described as atransition portion, transitioning from the first portion 302 to thesecond portion 304, e.g. by tapering from a larger cross section to thesmaller cross section of the second portion. An inlet aperture 308 maybe provided at the transition portion, for the gases to pass from thechamber 313 to the main gases path 301. The inlet may be formed as anannular opening extending around the first portion 302 of the main gasesflow path. The chamber may comprise an inlet (not shown in FIG. 10 ),allowing a flow of gases to enter the humidification chamber, the inletseparate from the main gases flow path so that gases enter thehumidification source before entering the main gases flow path via theinlet aperture 308.

In some embodiments, the third portion 303 may be integrally formed withat least one of the first 302 and second 304 portions and the gases flow310 may be generated by an aperture located in either the second portion304 or the third portion 303. In some embodiments, the humidificationchamber may be sealed and an aperture may be present in the firstportion 302 to generate a flow of gases from the main gases flow path301 into the humidification chamber 313.

In some embodiments, the inlet apertures of any of the humidificationsystems described above may comprise a valve, snorkel arrangement,membrane, filter, or the like configured to reduce the likelihood ofwater ingress into the gases flow path. The valve, membrane, or filtermay be configured to reduce the likelihood of water ingress into thegases flow path but to allow gases therethrough. The snorkel arrangementmay comprise a tortuous pathway that, in the case of where thehumidification system is tilted or inverted, reduces the likelihood offlow into the gases flow path.

FIG. 11 shows an embodiment comprising a humidification chamber 413 anda main gases flow path 401. The main gases flow path 401 comprisesfeatures configured to generate a gases flow 409 from the humidificationchamber 413 into the main gases flow 411, 412. The main gases flow path401 comprises a gases inlet 406, a first portion 402, a second portion404, and a gases outlet 405. Gases flow into the gases inlet 406 passesthrough the first and second portions 402, 404 and out the gases outlet405. The cross sectional area of the first portion 402 is greater thanthat of the second portion 404.

The gases flow path 411, 412 may comprise a transition portion 403. Thetransition portion 403 provides for a transition from the first portion402 to the second portion 404. The inlet aperture 408 is located in thesecond portion 404 and the outlet aperture 407 is located in the firstportion 402. The inlet aperture 408 generates a gases flow 409 from thehumidification chamber 413 into the main gases flow path 401. The outletaperture 408 generates a gases flow 410 from the main gases flow path401 into the humidification chamber. It is envisaged that the positionsof the first portion 402 and second portion 404 could be swapped.

The main gases flow path 1, 101, 201, 301, 401 may be formed in a lidcomponent of a humidification chamber, for example as depicted in FIGS.3, 6 and 9 . The lid component may seal the chamber 13, 113 but for theflow path through the chamber via the outlet aperture 107 and the inletaperture 108. In the embodiment of FIGS. 7 to 9 , the lid component mayprovide an inlet (not shown) to the chamber separate from the main gasesflow path, or the chamber may be provided with an inlet separate fromthe lid, e.g. via a side wall of the chamber. In some embodiments, themain gases flow path 1, 101, 201, 301, 401 may be provided in a tubularcomponent passing through a gases space of the chamber, for example asdepicted in the arrangements of FIGS. 10 and 11 , or may be formed in awall or base of the chamber.

In some embodiments, a connector part may comprise a main gases flowpath for connecting a humidification source that is remote from the maingases flow path. FIGS. 12A to 12F illustrate a gases flow connector part500 comprising a main gases flow path 501. The main gases flow path 501comprises an inlet portion 502, a neck portion 503, and an outletportion 504, as described in the earlier embodiments. The embodiment ofFIGS. 12A to 12F is similar to the embodiment of FIGS. 7 to 9 , in thatit has an inlet aperture 508 and is without an outlet aperture. However,in some embodiments an outlet aperture 7, 107, 407 may be provided, toallow a flow of gases from the main gases flow path to enter thehumidification source, as described in the embodiments of FIGS. 1 to 3,4 to 6 and 11 . An outlet aperture may be positioned within the inletportion 502, e.g. near to the inlet end 506 of the main gases flow path501. The inlet portion 502 is a first portion and the neck portion 503is a second portion. The first portion 502 comprises a larger crosssectional area than the second portion 503 so that with a flow of gases511, 512 through the main gases flow path 501 a high pressure region isgenerated in the first portion 502 and a low pressure region isgenerated in the second portion 503. With the inlet aperture 508 locatednear to the second region 503 the low pressure region draws a flow froma humidification source attached to or in communication with the inletaperture 508. The humidification source, such as a heated humidificationchamber may have an inlet (e.g. inlet 26 in FIG. 13 ) to draw a flow ofgases into the humidification source which then pass to the main gasesflow path via the inlet aperture 508, as described with reference to theembodiments of FIGS. 7 to 10 .

In the embodiment of FIGS. 12A to 12F, the inlet aperture 508 is near toa downstream end of the neck portion 503 (e.g. at or adjacent to thedownstream end). In some embodiments, the inlet aperture 508 may bewithin the neck portion or near to an upstream end of the neck portion.As illustrated in FIGS. 12D and 12F, in some embodiments the inletaperture 508 may comprise an annular cavity extending at least part wayaround the main gases flow path. In some embodiments the cavity mayextend fully around the main gases flow path. The annular cavity maycomprise a toroid cavity with a half cylinder cross section open intothe main gases flow path towards an outlet end of the main gases flowpath, as shown in FIGS. 12D and 12F. Such an arrangement directs a flowof humidified gases from the humidification source into the main gasesflow path in a direction of flow of gases 511, 512 through the maingases flow path from an inlet end to an outlet end of the main gasesflow path. This may help to disperse the humidified gases from thehumidification source in the gases flow through the main gases flowpath, and/or reduce turbulence of flow in the main gases flow pathcreated by mixing of the flow of gases from the humidification sourceinto the main gases flow path.

The gases flow connector part 500 of FIGS. 12A to 12F comprises ahumidification inlet portion 515 for connecting to a humidificationsource. For example, the humidification inlet portion 515 may form aconnector for connecting to a hose or conduit. A humidification sourceremote from the main gases flow path 501 may be connected to the maingases flow path 501 via a conduit connected to the inlet portion 515.The inlet portion 515 communicates with the main gases flow path 501 viathe inlet aperture 508. The gases flow part 500 may be a connector, forconnecting a humidification source into a respiratory system providing aflow of respiratory gases from a main gases source to a patient via apatient interface. FIG. 13 illustrates a humidification systemcomprising a flow source 20 connected to an inlet end 506 of theconnector 500 via a conduit 21. A humidification source 25 comprising ahumidification chamber 13 is connected to the humidification inlet 515of the connector 500 via a conduit 22. The humidification source 25 maybe remote from the gases flow source 20. In some embodiments, the flowsource 20 and the humidification source 25 may be remote from the maingases flow path 501 of the connector 500. The outlet end 505 of theconnector 500 is connected to a patient interface 30 to provide a flowof humidified gases to a patient 100. The connector 500 may be near toor directly connected to the patient interface 300, and/or may beconnected to the patient interface via a conduit 23. The connector 500may be a ‘T’ connector as illustrated, with the inlet portion 515 at aright angle to the main flow path 501. In an alternative embodiment theconnector may be a ‘Y’ connector. In some embodiments the flow source 20may comprise the main gases flow path 501, or the connector 500 may benear to the flow source 20.

In some embodiments, the system may comprise a valve 28 between thehumidification source 25 and the main gases flow path 501. The valve 28may vary a proportion of humidified gases added to the flow of gases inthe main gases flow path 501. For example a user may adjust the valve,or a controller may be provided to control the valve, for example thehumidification source may comprise a controller for controlling a flowrate of gases from the humidification source 25 to the main gases flowpath 501 by controlling valve 28.

In some embodiments, the connector 500 may comprise an outlet aperturefrom the main gases flow path and an inlet aperture to the main gasesflow path, as described above. In such an embodiment, the connector 500may comprise a humidification inlet portion 515 and a humidificationoutlet portion 516 in fluid communication with the inlet aperture andthe outlet aperture respectively. A humidification source outlet 27 anda humidification source inlet 26 may be connected to the humidificationinlet portion 515 and the humidification outlet portion 516 viarespective conduits 22, 24. In FIG. 13 the humidification outlet portion516 and conduit 24 are illustrated in dashed lines.

Again with reference to FIGS. 12A to 12F, in some embodiments astructure may be provided to cause gases flow 512 in the main gases flowpath 501 to swirl (for example swirl about a longitudinal axis of themain gases flow path). The structure causes swirling (e.g. a vortex) ofthe gases flow in the main gases flow path to help reduce disruption offlow (e.g. turbulence or stalling of flow or disruption of flow boundarylayers) caused by mixing of a flow of gases entering the main gases flowpath from the humidification source via the inlet aperture 508. Thestructure may comprise one or more vanes or baffles that interfere withthe gases flow to cause the flow to swirl. In the embodiment of FIGS.12A to 12F the structure comprises four vanes 518. The vanes may extendfrom a central member 119 to a side wall of the outlet portion 504and/or the neck portion 503 of the main gases flow path. The structuremay be within the inlet portion 502, the neck portion 503 or both. Insome less preferred embodiments, the structure may be within the outletportion 504. Preferably the structure is upstream of the inlet aperture508. In the illustrated embodiment the vanes 518 extend from near to aninlet end of the inlet portion 502 to near to an outlet end of thenecked portion 503. The structure 518 may be provided at or adjacent tothe inlet end 506 of the main gases flow path 501. The structure 518 maybe provided upstream to the inlet aperture 508. The central member 519may be coaxial with the main gases flow path. The vane or vanes 518 maybe curved to assist with spiraling the gases flow. A single vane may beprovided, for example a helical vane with an axis coaxial with the maingases flow.

In the embodiments of FIGS. 1 to 9 and 12A to 12F the main gases flowpath may be without one of the inlet portion and the outlet portion. Inother words, the neck portion may form an inlet or an outlet portion.

In the above described embodiments, the inlet aperture 8, 108, 208, 308,408, 508 may be described as an ‘injection aperture’ or ‘injectionport’, allowing gases from the humidification source to enter the maingases flow path. The outlet aperture 7, 107, 407 may be described as apressure equalization port, to avoid a vacuum in the humidificationsource as gases flow from the humidification source to the main gasesflow path via the inlet aperture. As described earlier, the outletaperture 7, 107, 407 and inlet aperture 8, 108, 408, 508 provide a shunt(e.g. parallel) or secondary flow path to divert a portion of the gasesflow in the main gases flow path from the main gases flow path throughthe humidification source and back into the main gases flow path. Theflow of gases through the humidification source from the outlet apertureto the inlet aperture is a secondary flow (parallel to or alongside) tothe flow of gases along the main gases flow path. As described earlier,in some embodiments, a humidification source inlet (e.g. an equalizationport) may be provided separate from the main gases flow path, to allow aflow of gases to enter the humidification source. In an embodimentwithout an outlet aperture between the main gases flow path and thehumidification source, a portion of a flow of gases through the maingases flow path 1, 101, 201, 301, 401, 501 does not enter thehumidification source. A flow through the humidification source from thehumidifier inlet to the main gases flow via the inlet aperture 8, 108,408 is a shunt (e.g. parallel) or secondary flow to the flow of gases inthe main gases flow path.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude these features, elements and/or states.

Conjunctive language, such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

While the above detailed description may have shown, described, andpointed out novel features as applied to various embodiments, it may beunderstood that various omissions, substitutions, and/or changes in theform and details of any particular embodiment may be made withoutdeparting from the spirit of the disclosure. As may be recognized,certain embodiments may be embodied within a form that does not provideall of the features and benefits set forth herein, as some features maybe used or practiced separately from others.

Additionally, features described in connection with one embodiment canbe incorporated into another of the disclosed embodiments, even if notexpressly discussed herein, and embodiments having the combination offeatures still fall within the scope of the disclosure. For example,features described above in connection with one embodiment can be usedwith a different embodiment described herein and the combination stillfall within the scope of the disclosure.

It should be understood that various features and aspects of thedisclosed embodiments can be combined with, or substituted for, oneanother in order to form varying modes of the embodiments of thedisclosure. Thus, it is intended that the scope of the disclosure hereinshould not be limited by the particular embodiments described above.Accordingly, unless otherwise stated, or unless clearly incompatible,each embodiment of this disclosure may comprise, additional to itsessential features described herein, one or more features as describedherein from each other embodiment disclosed herein.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of asubcombination.

Moreover, while operations may be depicted in the drawings or describedin the specification in a particular order, such operations need not beperformed in the particular order shown or in sequential order, or thatall operations be performed, to achieve desirable results. Otheroperations that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the described operations. Further, the operations may berearranged or reordered in other implementations. Those skilled in theart will appreciate that in some embodiments, the actual steps taken inthe processes illustrated and/or disclosed may differ from those shownin the figures. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added.

Furthermore, the features and attributes of the specific embodimentsdisclosed above may be combined in different ways to form additionalembodiments, all of which fall within the scope of the presentdisclosure. Also, the separation of various system components in theimplementations described above should not be understood as requiringsuch separation in all implementations, and it should be understood thatthe described components and systems can generally be integratedtogether in a single product or packaged into multiple products.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount. Asanother example, in certain embodiments, the terms “generally parallel”and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees,10 degrees, 5 degrees, 3 degrees, 1 degree, 0.1 degree, or otherwise.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise”, “comprising”, and thelike, are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense, that is to say, in the sense of“including, but not limited to”.

Reference to any prior art in this description is not, and should not betaken as, an acknowledgement or any form of suggestion that that priorart forms part of the common general knowledge in the field of endeavorin any country in the world.

The invention may also be said broadly to consist in the parts, elementsand features referred to or indicated in the description of theapplication, individually or collectively, in any or all combinations oftwo or more of said parts, elements or features.

Where, in the foregoing description, reference has been made to integersor components having known equivalents thereof, those integers areherein incorporated as if individually set forth. In addition, where theterm “substantially” or any of it's variants have been used as a word ofapproximation adjacent to a numerical value or range, it is intended toprovide sufficient flexibility in the adjacent numerical value or rangethat encompasses standard manufacturing tolerances and/or rounding tothe next significant figure, whichever is greater.

It should be noted that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the invention and withoutdiminishing its attendant advantages. For instance, various componentsmay be repositioned as desired. It is therefore intended that suchchanges and modifications be included within the scope of the invention.Moreover, not all of the features, aspects and advantages arenecessarily required to practice the present invention. Accordingly, thescope of the present invention is intended to be defined only by theclaims.

What is claimed is:
 1. A humidification system comprising: ahumidification chamber a main gases flow path comprising a venturistructure, wherein the venturi structure comprises: an upstream regionwith a first cross-sectional area, a narrowing transition region, anarrow region with a second cross-sectional area, a widening transitionregion, a downstream region with a third cross-sectional area, whereingases flow along the main gases flow path from the upstream region tothe downstream region, and wherein the venturi structure forms apressure differential between the gases in the upstream region and thegases in the narrow region; an inlet aperture positioned in the narrowregion of the main gases flow path, wherein the inlet aperture isconfigured to allow humidified gases to pass from the humidificationchamber to the main gases flow path; an outlet aperture positioned inthe upstream region of the main gases flow path, wherein the outletaperture is configured to allow gases to pass from the main gases flowpath to the humidification chamber; and a structure configured to varythe cross-sectional area of the narrow region of the main gases flowpath.
 2. The humidification system of claim 1, wherein the thirdcross-sectional area of the downstream region is smaller than the firstcross-sectional area of the upstream region.
 3. The humidificationsystem of claim 1, wherein the third cross-sectional area of thedownstream region is the same as the first cross-sectional area of theupstream region.
 4. The humidification system of claim 1, wherein thethird cross-sectional area of the downstream region is greater than thefirst cross-sectional area of the upstream region.
 5. The humidificationsystem of claim 1, wherein the humidification chamber further comprisesa heater configured to warm a liquid in the humidification chamber,wherein the heater comprises a heater plate positioned at a bottom ofthe humidification chamber.
 6. The humidification system of claim 1,wherein the narrowing transition region has a constant pitch.
 7. Thehumidification system of claim 1, wherein the narrowing transitionregion has a variable pitch.
 8. The humidification system of claim 1,wherein the widening transition region has a variable pitch.
 9. Thehumidification system of claim 1, further comprising a valve positionedbetween the humidification chamber and the main gases flow path, whereinthe valve is configured to change at least one of pressure, velocity,flow rate, and a flow profile of a flow of gases from the humidificationsource to the main gases flow path.
 10. A humidification systemcomprising: a humidification chamber a main gases flow path comprising aventuri structure, wherein the venturi structure comprises: an upstreamregion with a first cross-sectional area, a narrowing transition region,a narrow region with a second cross-sectional area, a wideningtransition region, a downstream region with a third cross-sectionalarea, wherein gases flow along the main gases flow path from theupstream region to the downstream region, and wherein the venturistructure forms a pressure differential between the gases in theupstream region and the gases in the narrow region; an inlet aperturepositioned in the narrow region of the main gases flow path, wherein theinlet aperture is configured to allow humidified gases to pass from thehumidification chamber to the main gases flow path; an outlet aperturepositioned in the upstream region of the main gases flow path, whereinthe outlet aperture is configured to allow gases to pass from the maingases flow path to the humidification chamber; and a structureconfigured to vary the cross-sectional area of the upstream region ofthe main gases flow path.
 11. The humidification system of claim 10,wherein the third cross-sectional area of the downstream region issmaller than the first cross-sectional area of the upstream region. 12.The humidification system of claim 10, wherein the third cross-sectionalarea of the downstream region is the same as the first cross-sectionalarea of the upstream region.
 13. The humidification system of claim 10,wherein the third cross-sectional area of the downstream region isgreater than the first cross-sectional area of the upstream region. 14.The humidification system of claim 10, wherein the humidificationchamber further comprises a heater configured to warm a liquid in thehumidification chamber, wherein the heater comprises a heater platepositioned at a bottom of the humidification chamber.
 15. Thehumidification system of claim 10, wherein the narrowing transitionregion has a constant pitch.
 16. The humidification system of claim 10,wherein the narrowing transition region has a variable pitch.
 17. Thehumidification system of claim 10, wherein the widening transitionregion has a variable pitch.
 18. The humidification system of claim 10,further comprising a valve positioned between the humidification chamberand the main gases flow path, wherein the valve is configured to changeat least one of pressure, velocity, flow rate, and a flow profile of aflow of gases from the humidification source to the main gases flowpath.